1. Field of the Invention
The present invention relates to a nitride semiconductor and a method for manufacturing the same.
2. Description of the Related Art
A GaN group nitride semiconductor is one of widely known nitride semiconductors according to the related art. The GaN group nitride semiconductors have been used in a high speed switch or a high power device such as a blue or a green light emitting diode (LED), a metal semiconductor FET (MESFET) and a high electron mobility transistor (HEMT).
Such a GaN group nitride semiconductor according to the related art is generally grown on a sapphire substrate. Then, a polycrystalline thin film is grown on the sapphire substrate at a low temperature as a buffer layer. After forming the buffer layer, an un-doped GaN layer and a Si doped n-GaN layer are sequentially formed on the buffer layer at a high temperature.
Then, the n-GaN layer functions as a first electrode contact layer, and a magnesium doped P-GaN layer is formed on the first electrode contact layer as a second electrode contact layer so as to manufacture the GaN group nitride semiconductor.
Especially, in the field of a light emitting device such as a light emitting diode and a semiconductor laser diode among the application fields of the GaN group nitride semiconductor according to the related art, a P-type nitride semiconductor emitting a blue light has been receiving attention. The P-type nitride semiconductor is a GaN group nitride semiconductor with the group 2 elements such as magnesium or zinc disposed on the location of the group 3 elements Ga.
In order to manufacture the P-type nitride semiconductor among the GaN group nitride semiconductors according to the related art as shown in FIG. 1, a doping method is performed to arrange the group 2 element such as magnesium on the location of the group 3 element such as Ga. The arranged group 2 element, magnesium, is coupled with adjacent atoms so as to generate a hole. The generated hole functions as an acceptor.
However, it is very difficult for the P-type nitride semiconductor according to the related art to have high conductivity because the magnesium is combined with hydrogen H. Therefore, a thermal annealing process is additionally required to separate the coupling of the magnesium and the hydrogen according to the related art.
According to the related art, only about 1% of the doped magnesium functions as the acceptor. That is, about 99% of the doped magnesium is remained inside the semiconductor crystalline layer after combined with the hydrogen. It degrades the crystallinity thereof.